Simplify bootstrap and generate code (#514)

- We now automatically generate bootstrap_gen.py file from the list of instrumentations present in the source tree.
- Bootstrap command now uses consumes this auto-generated list instead of keeping it's own local copy.
- We no longer uninstall packages before installing them as instrumentation package no longer specify libraries as dependencies so the edge cases are no longer there.
- We no longer try to install an incompatible version or force upgrade/downgrade an installed version. This used to leave systems in broken states which should happen no more.

scripts/generate_instrumentation_bootstrap.py

@@ -0,0 +1,98 @@
+#!/usr/bin/env python3
+
+# Copyright The OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import ast
+import logging
+import os
+import subprocess
+
+import astor
+import pkg_resources
+from otel_packaging import (
+    get_instrumentation_packages,
+    root_path,
+    scripts_path,
+)
+
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger("instrumentation_list_generator")
+
+_auto_generation_msg = """
+# DO NOT EDIT. THIS FILE WAS AUTOGENERATED FROM templates/{source}.
+# RUN `python scripts/generate_setup.py` TO REGENERATE.
+"""
+
+_template = """
+{header}
+
+# DO NOT EDIT. THIS FILE WAS AUTOGENERATED FROM INSTRUMENTATION PACKAGES.
+# RUN `python scripts/generate_instrumentation_bootstrap.py` TO REGENERATE.
+
+{source}
+"""
+
+_source_tmpl = """
+libraries = {}
+default_instrumentations = []
+"""
+
+
+gen_path = os.path.join(
+    root_path,
+    "opentelemetry-instrumentation",
+    "src",
+    "opentelemetry",
+    "instrumentation",
+    "bootstrap_gen.py",
+)
+
+
+def main():
+    # pylint: disable=no-member
+    default_instrumentations = ast.List(elts=[])
+    libraries = ast.Dict(keys=[], values=[])
+    for pkg in get_instrumentation_packages():
+        if not pkg["instruments"]:
+            default_instrumentations.elts.append(ast.Str(pkg["requirement"]))
+        for target_pkg in pkg["instruments"]:
+            parsed = pkg_resources.Requirement.parse(target_pkg)
+            libraries.keys.append(ast.Str(parsed.name))
+            libraries.values.append(
+                ast.Dict(
+                    keys=[ast.Str("library"), ast.Str("instrumentation")],
+                    values=[ast.Str(target_pkg), ast.Str(pkg["requirement"])],
+                )
+            )
+
+    tree = ast.parse(_source_tmpl)
+    tree.body[0].value = libraries
+    tree.body[1].value = default_instrumentations
+    source = astor.to_source(tree)
+
+    with open(
+        os.path.join(scripts_path, "license_header.txt"), "r"
+    ) as header_file:
+        header = header_file.read()
+        source = _template.format(header=header, source=source)
+
+    with open(gen_path, "w") as gen_file:
+        gen_file.write(source)
+
+    subprocess.run(["black", "-q", gen_path], check=True)
+
+
+if __name__ == "__main__":
+    main()